A fuel cell unit of this type has a current collection mechanism for drawing a current from an end of a fuel cell stack to the outside of the fuel cell unit. As the current collection mechanism, a plate-shaped or spring-shaped metal, alloy, or a conductive ceramic is usually used.
In this case, however, since the surface of the fuel cell stack and the surface of the current collection mechanism have small irregularities or a warpage, a conductive material, such as a metal, an alloy, or a conductive ceramic, needs to be separately provided to fill a small gap formed between the fuel cell stack and the current collection mechanism.
This causes the current collection mechanism and the conductive material to be exposed to a high-temperature oxidizing atmosphere, and thus the current collection mechanism and the conductive material are required to have not only a heat resistance, but also a resistance to the oxidizing atmosphere. Likewise, the current collection mechanism and the conductive material may also be exposed to a high-temperature reducing atmosphere. In this case, the current collection mechanism and the conductive material are required to have a resistance to the reducing atmosphere, instead of having a resistance to the oxidizing atmosphere.
Generally, there is a difference between the thermal expansion coefficients of the current collection mechanism, the conductive material, and separators constituting the fuel cell stack, which often causes a problem of destruction of conductive paths due to a thermal stress. Accordingly, in many cases, a system is employed in which various load mechanisms such as a spring mechanism, a screwing mechanism, and a bind mechanism, are separately provided and a load is applied so as to bring the current collection mechanism into close contact with the fuel cell stack.
PTL 1: International Publication No. WO 2010/038869